Last week, I discussed how biodiesels carry promise as a transitional fuel in a more environmentally conscious economy. However, biodiesels do not seem a viable long-term alternative to gasoline or diesel due to its difficulty in fulfilling demand, not to mention the fact that it can only mitigate emissions—not eliminate them. There is another technology that could prove to be a fitting long-term solution, and that technology is the hydrogen fuel cell.
Fuel cells are similar to batteries, as they convert chemical energy into electrical energy. A fuel cell consists of a conducting material (electrolyte), pressed between two catalysts: an anode and a diode. In fuel cells which run on hydrogen (which are not the only kind of fuel cell), the assembly pumps hydrogen gas over the anode and oxygen (usually from air) over the diode. The anode strips the electrons from the gaseous hydrogen, separating it into bare, positively charged hydrogen nuclei and free electrons. The electrolyte conducts the electrons away—producing an electrical current—while pumping the bare nuclei into the diode. With the aid of the diode, the fuel cell oxidizes the hydrogen to create water, which is flushed away as exhaust. (see How Stuff Works, c. 2013)
Hydrogen fuel cells have the potential to be more efficient than combustion engines, with 40-60% of the energy remaining after waste heat, as opposed to diesel’s 22%. (Wikipedia, 2013) In practice, this gap is narrower, but the technology shows promise. Furthermore, since the reaction produces water as waste instead of CO2, carbon monoxide, nitrous oxide or the other pollutants that result from combustion engines, the harmful emissions from a car (or factory) running on hydrogen would be zero.
A large number of technological hurdles exist to making this technology affordable for individuals to use, from safe storage of hydrogen to cell durability to hydrogen production. The last of these is the most pressing issue, as hydrogen can be difficult to produce in a manner that is efficient, economical and ecologically sound. The standard method involves a reaction between steam and methane, which produces substantial amounts of carbon dioxide. (see Wikipedia, 2013) Needless to say, this quite nearly defeats the purpose of using hydrogen as a fuel in the first place.
However, all of these technological issues appear surmountable. The Department of Energy’s fuel cell initiative appears to have made some progress in reducing the cost of producing fuel cells, and private companies seem to have fuel-cell automobiles ready for production. The traditional process of producing hydrogen from steam reforming can be made more “green,” in theory, by sequestering CO2 byproducts. Alternatives to steam reforming abound, including the development of an artificial leaf that uses solar energy to split water into hydrogen and oxygen.
The hard sciences give us reason to hold an optimistic view of the utility of hydrogen fuel cells. It is economics—the dismal science—which gives us reason to cringe. The main reason we have yet to find hydrogen cars roaming the streets is infrastructure. The Department of Energy's progress report indicates the existence of twenty-five hydrogen fuel stations in the United States. As with biodiesel, the question isn’t “Can we make a fuel cell?” It is simply: “Where do I fuel up?”
And there, ladies and gentlemen, lies the rub.